As manufacturing method for spun-bonded nonwoven fabric, there are known the opened type method, which comprises quenching melt-spun filaments with quench air, drawing the filaments by passing them through round air guns or slit air guns and then spreading them onto a mesh belt using a separator or an oscillator, and the closed type method, which comprises quenching the melt-spun filaments with quench air fed to a quenching chamber, drawing the filaments through nozzles by reusing the quench air as drawing air and spreading the filaments onto a mesh belt, as described in, e.g., Japanese Patent Laid-Open No. 57-35053 or 60-155765.
In the method for manufacturing spun-bonded nonwoven fabric, filaments are quenched by blowing quench air against a multiple number of continuous filaments melt-spun through spinning nozzles. When an amount of the filaments to be discharged is increased with an attempt to achieve better productivity, it becomes necessary to supply a sufficient volume of quench air correspondingly to the increased amount. Where the quench air is poorly supplied, quenching of filaments is insufficient to cause the mass (shot) of resin on a web; in the opened type method, plugging occurs in a drawing device such as air guns, etc. On the other hand, when the quench air is supplied excessively, breakage of filaments would take place due to supercooling.
In applying the closed type method, good filaments are obtained in a simple process and webs with an excellent uniformity can be produced. However the filaments are drawn by the quench air fed to a quenching chamber, that is, quench air and drawing air are commonly used, so that quenching and drawing can not proceed independently. For this reason, where it is attempted to increase a drawing tension by supplying a larger amount of drawing air thereby to reduce a filament diameter, a larger amount of quench air is supplied at the same time, which would result in the breakage of filaments.
An object of the present invention is to provide a method for manufacturing spun-bonded nonwoven fabrics, which causes no breakage of filaments even by supplying a large amount of quench air, can reduce the diameter of a filament without losing productivity and can produce nonwoven fabrics stably. Another object of the invention is to provide an apparatus suitable for the method above.